Capacitors may be sealed in a number of ways. A simple, inexpensive procedure is to solder a lead to a conductive coating and dip the entire device in hardenable low density plastic, such as epoxy resin. This type of seal is subject to environmental conditions, however, because the plastic is not impervious to moisture.
In a second, superior sealing process, the capacitor is inserted in a solderable metal casing or can. The conductive coating is electrically and mechanically connected with the casing by imbedding the capacitor in soft solder. A connecting wire is attached to the bottom of the casing to serve as the external cathode lead. The anode wire with its attached input lead extends to an opening at the opposite end of the casing. This opening can be hermetically sealed by providing a metal-glass-metal cover. Both the metal and anode wire and the metal casing are soldered to the respective metal portions of the cover, with a glass providing an insulation between the anode wire and the casing.
And, in a third sealing process, the expensive metal-glass-metal cover is replaced by a hardenable plastic which fills the open end of the casing. Although this type of seal is less expensive, the plastic itself is pervious, particularly at the interface between metal and plastic: namely, along the anode wire lead and along the casing wall. Moisture may reach the inside of the casing via the interface causing failure of the capacitor.
With respect to wrapping of capacitors, U.S. Pat. No. 5,032,950 which issued on Jul. 16, 1991 is directed to a cuff tape wrap and fill capacitor. The capacitor comprises a press capacitor having conductor foil cuffs. The cuffs are provided either in the form of bands or in the form of folds. The cuffs may be prepared from any flexible conducting material. The ends of the capacitor are sealed with an appropriate sealing means such as high temperature epoxy of silicon resin.